A gobo is a device that shapes light. Many lighting devices use a holder for multiple gobos. The holder allows selection of one of the gobos to be placed into the beam of the light beam. It also allows simultaneous rotation of all these gobos, including the one in the light beam.
For example, U.S. Pat. No. 5,402,326 shows a device with a gobo wheel, having five gobos and an open hole thereon. The gobo wheel holds the five gobos, and the gobo wheel is rotatable to allow any of the five gobos to be placed within the “optical train”, which is the train of light that passes from the light bulb to the output beam of the light. In addition, the gobo wheels are rotatable as part of an effect of a rotating gobo. The central gear arrangement causes all of the gobos to be rotated simultaneously. When the central gear is actuated, each of the five gobos simultaneously rotate.